An internal combustion engine produces power by converting combustion pressure formed in a cylinder to rotational torque of a crankshaft. The combustion pressure in the cylinder is time variant depending on crank angle. That is, an output torque of the crankshaft (i.e., engine torque) is not constant and it fluctuates depending on the crank angle. Therefore, in order to prevent unstableness of the engine torque, a flywheel is mounted to an end of the crankshaft.
When a mass of the flywheel is increased, acceleration characteristics of the engine deteriorate. To the contrary, when the mass of the flywheel is reduced, the engine torque may become unstable. In this respect, the rotational inertia of a flywheel is designed such that acceleration characteristics of an engine and stabilization of engine torque are appropriately compromised.
An optimal compromised point may vary depending on engine speed. Therefore, when a flywheel is designed such that inertia of the flywheel is increased at a low engine speed so that an engine operation is stabilized, and the inertia is decreased at a high engine speed so that performance of the engine is enhanced, it may promise simultaneous achievement of stabilization of engine operation and an increase in fuel mileage.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known in this country to a person of ordinary skill in the art.